Fix handling of consecutive _send* calls
Fix handling of consecutive _send* calls

Previously, two consecutive calls of _send* functions will execute
the first one only. This commit fixes this problem.

Example reproducing the bug:

  spawn(...)
    .expect('prompt')
    .sendLine('response')
    .sendEof()
    .run(...);

stacywile/spectcl,ViaSat/spectcl,stacywile/spectcl,ryanbmilbourne/spectcl,ryanbmilbourne/spectcl